1. Field of the Invention
The invention relates to a device for detecting flames with detectors and to a method for detecting flames by means of detectors.
The invention can be used wherever reliable recognition of flames, independent of disruptive influence variables such as ambient temperature, interference radiation, or the viewing angle of the recording or detection device is required.
2. The Prior Art
For detecting flames using alarms or fire extinguishing devices, it is known to detect the wavelength of the flames with a detector, to convert it to an electrical signal, and to pass this signal on to a subsequent evaluation device for evaluating the detector signal.
EP 0 926 647 B1 describes a fire detection method for recognizing a fire in a monitored region, in which method sensors are used, which react to a radiation within a specific bandwidth.
No consideration of the angle and temperature dependence takes place. There is no provision for preventing the three wavelength ranges from overlapping at minimal/maximal temperature and at a maximal incidence angle. The cross-correlation is used. This is not necessary in the present invention, because of the synchronous sampling of the signals and the symmetrical structure.
Austrian Application No. AT381406 B and Swiss Application No. CH000000628171A show a similar device, in which only two sensors are used, and the bearing frequency is filtered out by means of a hardware circuit, a bypass. No consideration of the angle dependence takes place. Also, no digital signal processing by way of a microcontroller is described.
German Patent Application No. DE 102008024496A1, a device for detecting flames is described, in which two sensors are present. This device is also not suitable for taking the angle dependence into consideration. Also, no digital signal processing by way of a microcontroller takes place.
German Patent Application No. DE 3140678 A1 describes an infrared (IR) flame alarm having three IR sensors. Minimization of false alarms is only accomplished with regard to the masking of IR radiation from sources in the range of 2 to 5 μm, which do not represent flames. No solutions are described that use identical detectors with identical signal processing for simple masking of interference variables. It is a disadvantage of this solution that electromagnetic radiation, for example, in the MHz or GHz frequency range, for example, which can also be coupled into the electronic circuit after the sensors, can lead to a false alarm. No solutions are described that can prevent such false alarms
U.S. Pat. No. 4,233,596 describes an infrared measurement device having two IR sensors with different wavelengths, in order to detect black smoke in a useful flame (flare). It is a disadvantage that this device cannot be used for recognition of flames that occur randomly during a fire event, to minimize false alarms.
It is a problem in the case of the known devices for detecting flames that distortions of the detected wavelengths occur due to interference of influence variables such as the ambient temperature, interference radiation, for example sun radiation, or the viewing angle at which the detection device is disposed, so that due to a false alarm, triggering of the alarm device or the fire extinguishing device could occur. Furthermore, it is problematic that in the known devices, complicated calculation methods and long measurement cycles become necessary for partial compensation of these interference variables. This is connected with a high consumption of energy and a long reaction time for flame recognition.
US Patent Application No. 2005/195086 A1 describes an IR flame alarm having three different IR receiver elements. The signals of the detectors go directly, serially into the processor. This means that no synchronous signal pickup at the same time is possible. No solution is described that uses identical detectors with identical signal processing for simple masking of interference variables that lead to false alarms. In particular, the description that the signals of the detectors go directly, serially into the processor shows that no synchronous signal pickup at the same time is possible.